Subject: Re: [PATCH iproute2-next 1/2] dcb: add new pcp-prio parameter to dcb app

From: Petr Machata <[email-masked]>
Date: Thu, 24 Nov 2022 16:30:41 +0100

This looks good to me overall, I just have a few nits.

Daniel Machon <[email-masked]> writes:

> Add new pcp-prio parameter to the app subcommand, which can be used to
> classify traffic based on PCP and DEI from the VLAN header. PCP and DEI
> is specified in a combination of numerical and symbolic form, where 'de'
> (as specified in the PCP Encoding Table, 802.1Q) means DEI=1.
>
> Map PCP 1 and DEI 0 to priority 1 $ dcb app add dev eth0 pcp-prio 1:1
>
> Map PCP 1 and DEI 1 to priority 1 $ dcb app add dev eth0 pcp-prio 1de:1
>
> Internally, PCP and DEI is encoded in the protocol field of the dcb_app
> struct. Each combination of PCP and DEI maps to a priority, thus needing
> a range of  0-15. A well formed dcb_app entry for PCP/DEI
> prioritization, could look like:
>
>     struct dcb_app pcp = {
>         .selector = DCB_APP_SEL_PCP,
> 	.priority = 7,
>         .protocol = 15
>     }
>
> For mapping PCP=7 and DEI=1 to Prio=7.
>
> Also, two helper functions for translating between std and non-std APP
> selectors, have been added to dcb_app.c and exposed through dcb.h.

Could you include an example or two of how PCP is configured? E.g. the
following was part of the dcb-app submission:

    # dcb app add dev eni1np1 dscp-prio 0:0 CS3:3 CS6:6
    # dcb app show dev eni1np1
    dscp-prio 0:0 CS3:3 CS6:6

> Signed-off-by: Daniel Machon <[email-masked]>
> ---
>  dcb/dcb.h          |   3 +
>  dcb/dcb_app.c      | 138 +++++++++++++++++++++++++++++++++++++++++++--
>  man/man8/dcb-app.8 |  27 +++++++++
>  3 files changed, 162 insertions(+), 6 deletions(-)
>
> diff --git a/dcb/dcb.h b/dcb/dcb.h
> index 244c3d3c30e3..05eddcbbcfdf 100644
> --- a/dcb/dcb.h
> +++ b/dcb/dcb.h
> @@ -57,6 +57,9 @@ void dcb_print_array_kw(const __u8 *array, size_t array_size,
>  /* dcb_app.c */
>  
>  int dcb_cmd_app(struct dcb *dcb, int argc, char **argv);
> +enum ieee_attrs_app dcb_app_attr_type_get(__u8 selector);
> +bool dcb_app_attr_type_validate(enum ieee_attrs_app type);
> +bool dcb_app_selector_validate(enum ieee_attrs_app type, __u8 selector);
>  
>  /* dcb_buffer.c */
>  
> diff --git a/dcb/dcb_app.c b/dcb/dcb_app.c
> index dad34554017a..0d4a82e1e502 100644
> --- a/dcb/dcb_app.c
> +++ b/dcb/dcb_app.c
> @@ -10,6 +10,16 @@
>  #include "utils.h"
>  #include "rt_names.h"
>  
> +static const char *const pcp_names[16] = {
> +	"0",   "1",   "2",   "3",   "4",   "5",   "6",   "7",
> +	"0de", "1de", "2de", "3de", "4de", "5de", "6de", "7de"
> +};
> +
> +static const char *const ieee_attrs_app_names[__DCB_ATTR_IEEE_APP_MAX] = {
> +	[DCB_ATTR_IEEE_APP] = "DCB_ATTR_IEEE_APP",
> +	[DCB_ATTR_DCB_APP] = "DCB_ATTR_DCB_APP"
> +};
> +
>  static void dcb_app_help_add(void)
>  {
>  	fprintf(stderr,
> @@ -20,11 +30,13 @@ static void dcb_app_help_add(void)
>  		"           [ dgram-port-prio PORT:PRIO ]\n"
>  		"           [ port-prio PORT:PRIO ]\n"
>  		"           [ dscp-prio INTEGER:PRIO ]\n"
> +		"           [ pcp-prio INTEGER:PRIO ]\n"

This should say PCP:PRIO, not INTEGER:PRIO.

>  		"\n"
>  		" where PRIO := { 0 .. 7 }\n"
>  		"       ET := { 0x600 .. 0xffff }\n"
>  		"       PORT := { 1 .. 65535 }\n"
>  		"       DSCP := { 0 .. 63 }\n"
> +		"       PCP := { 0(de) .. 7(de) }\n"
>  		"\n"
>  	);
>  }
> @@ -39,6 +51,7 @@ static void dcb_app_help_show_flush(void)
>  		"           [ dgram-port-prio ]\n"
>  		"           [ port-prio ]\n"
>  		"           [ dscp-prio ]\n"
> +		"           [ pcp-prio ]\n"
>  		"\n"
>  	);
>  }
> @@ -58,6 +71,38 @@ struct dcb_app_table {
>  	size_t n_apps;
>  };
>  
> +enum ieee_attrs_app dcb_app_attr_type_get(__u8 selector)
> +{
> +	switch (selector) {
> +	case IEEE_8021QAZ_APP_SEL_ETHERTYPE:
> +	case IEEE_8021QAZ_APP_SEL_STREAM:
> +	case IEEE_8021QAZ_APP_SEL_DGRAM:
> +	case IEEE_8021QAZ_APP_SEL_ANY:
> +	case IEEE_8021QAZ_APP_SEL_DSCP:
> +		return DCB_ATTR_IEEE_APP;
> +	case DCB_APP_SEL_PCP:
> +		return DCB_ATTR_DCB_APP;
> +	default:
> +		return DCB_ATTR_IEEE_APP_UNSPEC;
> +	}
> +}
> +
> +bool dcb_app_attr_type_validate(enum ieee_attrs_app type)
> +{
> +	switch (type) {
> +	case DCB_ATTR_IEEE_APP:
> +	case DCB_ATTR_DCB_APP:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +bool dcb_app_selector_validate(enum ieee_attrs_app type, __u8 selector)
> +{
> +	return dcb_app_attr_type_get(selector) == type;
> +}
> +
>  static void dcb_app_table_fini(struct dcb_app_table *tab)
>  {
>  	free(tab->apps);
> @@ -213,6 +258,32 @@ static int dcb_app_parse_mapping_ethtype_prio(__u32 key, char *value, void *data
>  				 dcb_app_parse_mapping_cb, data);
>  }
>  
> +static int dcb_app_parse_pcp(__u32 *key, const char *arg)
> +{
> +	int ret, res;
> +
> +	res = parse_one_of("pcp-names", arg, pcp_names,
> +			   ARRAY_SIZE(pcp_names), &ret);
> +	if (ret < 0)
> +		return ret;
> +
> +	*key = res;
> +
> +	return 0;
> +}
> +
> +static int dcb_app_parse_mapping_pcp_prio(__u32 key, char *value, void *data)
> +{
> +	__u8 prio;
> +
> +	if (get_u8(&prio, value, 0))
> +		return -EINVAL;
> +
> +	return dcb_parse_mapping("PCP", key, 15,
> +				 "PRIO", prio, IEEE_8021QAZ_MAX_TCS - 1,
> +				 dcb_app_parse_mapping_cb, data);
> +}
> +
>  static int dcb_app_parse_dscp(__u32 *key, const char *arg)
>  {
>  	if (parse_mapping_num_all(key, arg) == 0)
> @@ -309,6 +380,11 @@ static bool dcb_app_is_dscp(const struct dcb_app *app)
>  	return app->selector == IEEE_8021QAZ_APP_SEL_DSCP;
>  }
>  
> +static bool dcb_app_is_pcp(const struct dcb_app *app)
> +{
> +	return app->selector == DCB_APP_SEL_PCP;
> +}
> +
>  static bool dcb_app_is_stream_port(const struct dcb_app *app)
>  {
>  	return app->selector == IEEE_8021QAZ_APP_SEL_STREAM;
> @@ -344,6 +420,17 @@ static int dcb_app_print_key_dscp(__u16 protocol)
>  	return print_uint(PRINT_ANY, NULL, "%d:", protocol);
>  }
>  
> +static int dcb_app_print_key_pcp(__u16 protocol)
> +{
> +	/* Print in numerical form, if protocol value is out-of-range */
> +	if (protocol > 15) {
> +		fprintf(stderr, "Unknown PCP key: %d\n", protocol);
> +		return print_uint(PRINT_ANY, NULL, "%d:", protocol);
> +	}
> +
> +	return print_string(PRINT_ANY, NULL, "%s:", pcp_names[protocol]);
> +}
> +
>  static void dcb_app_print_filtered(const struct dcb_app_table *tab,
>  				   bool (*filter)(const struct dcb_app *),
>  				   int (*print_key)(__u16 protocol),
> @@ -382,6 +469,15 @@ static void dcb_app_print_ethtype_prio(const struct dcb_app_table *tab)
>  			       "ethtype_prio", "ethtype-prio");
>  }
>  
> +static void dcb_app_print_pcp_prio(const struct dcb *dcb,
> +				   const struct dcb_app_table *tab)
> +{
> +	dcb_app_print_filtered(tab, dcb_app_is_pcp,
> +			       dcb->numeric ? dcb_app_print_key_dec
> +					    : dcb_app_print_key_pcp,
> +			       "pcp_prio", "pcp-prio");
> +}
> +
>  static void dcb_app_print_dscp_prio(const struct dcb *dcb,
>  				    const struct dcb_app_table *tab)
>  {
> @@ -439,26 +535,41 @@ static void dcb_app_print(const struct dcb *dcb, const struct dcb_app_table *tab
>  	dcb_app_print_stream_port_prio(tab);
>  	dcb_app_print_dgram_port_prio(tab);
>  	dcb_app_print_port_prio(tab);
> +	dcb_app_print_pcp_prio(dcb, tab);
>  }
>  
>  static int dcb_app_get_table_attr_cb(const struct nlattr *attr, void *data)
>  {
>  	struct dcb_app_table *tab = data;
>  	struct dcb_app *app;
> +	uint16_t type;
>  	int ret;
>  
> -	if (mnl_attr_get_type(attr) != DCB_ATTR_IEEE_APP) {
> -		fprintf(stderr, "Unknown attribute in DCB_ATTR_IEEE_APP_TABLE: %d\n",
> -			mnl_attr_get_type(attr));
> +	type = mnl_attr_get_type(attr);
> +
> +	if (!dcb_app_attr_type_validate(type)) {
> +		fprintf(stderr,
> +			"Unknown attribute in DCB_ATTR_IEEE_APP_TABLE: %d\n",
> +			type);
>  		return MNL_CB_OK;
>  	}
>  	if (mnl_attr_get_payload_len(attr) < sizeof(struct dcb_app)) {
> -		fprintf(stderr, "DCB_ATTR_IEEE_APP payload expected to have size %zd, not %d\n",
> -			sizeof(struct dcb_app), mnl_attr_get_payload_len(attr));
> +		fprintf(stderr,
> +			"%s payload expected to have size %zd, not %d\n",
> +			ieee_attrs_app_names[type], sizeof(struct dcb_app),
> +			mnl_attr_get_payload_len(attr));
>  		return MNL_CB_OK;
>  	}
>  
>  	app = mnl_attr_get_payload(attr);
> +
> +	/* Check that selector is encapsulated in the right attribute */
> +	if (!dcb_app_selector_validate(type, app->selector)) {
> +		fprintf(stderr, "Wrong selector for type: %s\n",
> +			ieee_attrs_app_names[type]);
> +		return MNL_CB_OK;
> +	}
> +
>  	ret = dcb_app_table_push(tab, app);
>  	if (ret != 0)
>  		return MNL_CB_ERROR;
> @@ -491,6 +602,7 @@ struct dcb_app_add_del {
>  static int dcb_app_add_del_cb(struct dcb *dcb, struct nlmsghdr *nlh, void *data)
>  {
>  	struct dcb_app_add_del *add_del = data;
> +	enum ieee_attrs_app type;
>  	struct nlattr *nest;
>  	size_t i;
>  
> @@ -498,9 +610,10 @@ static int dcb_app_add_del_cb(struct dcb *dcb, struct nlmsghdr *nlh, void *data)
>  
>  	for (i = 0; i < add_del->tab->n_apps; i++) {
>  		const struct dcb_app *app = &add_del->tab->apps[i];
> +		type = dcb_app_attr_type_get(app->selector);
>  
>  		if (add_del->filter == NULL || add_del->filter(app))
> -			mnl_attr_put(nlh, DCB_ATTR_IEEE_APP, sizeof(*app), app);
> +			mnl_attr_put(nlh, type, sizeof(*app), app);
>  	}
>  
>  	mnl_attr_nest_end(nlh, nest);
> @@ -577,6 +690,12 @@ static int dcb_cmd_app_parse_add_del(struct dcb *dcb, const char *dev,
>  			ret = parse_mapping(&argc, &argv, false,
>  					    &dcb_app_parse_mapping_port_prio,
>  					    &pm);
> +		} else if (strcmp(*argv, "pcp-prio") == 0) {
> +			NEXT_ARG();
> +			pm.selector = DCB_APP_SEL_PCP;
> +			ret = parse_mapping_gen(&argc, &argv, &dcb_app_parse_pcp,
> +						&dcb_app_parse_mapping_pcp_prio,
> +						&pm);
>  		} else {
>  			fprintf(stderr, "What is \"%s\"?\n", *argv);
>  			dcb_app_help_add();
> @@ -656,6 +775,8 @@ static int dcb_cmd_app_show(struct dcb *dcb, const char *dev, int argc, char **a
>  			dcb_app_print_port_prio(&tab);
>  		} else if (matches(*argv, "default-prio") == 0) {
>  			dcb_app_print_default_prio(&tab);
> +		} else if (strcmp(*argv, "pcp-prio") == 0) {
> +			dcb_app_print_pcp_prio(dcb, &tab);
>  		} else {
>  			fprintf(stderr, "What is \"%s\"?\n", *argv);
>  			dcb_app_help_show_flush();
> @@ -705,6 +826,11 @@ static int dcb_cmd_app_flush(struct dcb *dcb, const char *dev, int argc, char **
>  					      &dcb_app_is_dscp);
>  			if (ret != 0)
>  				goto out;
> +		} else if (strcmp(*argv, "pcp-prio") == 0) {
> +			ret = dcb_app_add_del(dcb, dev, DCB_CMD_IEEE_DEL, &tab,
> +					      &dcb_app_is_pcp);
> +			if (ret != 0)
> +				goto out;
>  		} else {
>  			fprintf(stderr, "What is \"%s\"?\n", *argv);
>  			dcb_app_help_show_flush();
> diff --git a/man/man8/dcb-app.8 b/man/man8/dcb-app.8
> index 9780fe4b60fa..054ba9801d81 100644
> --- a/man/man8/dcb-app.8
> +++ b/man/man8/dcb-app.8
> @@ -23,6 +23,7 @@ the DCB (Data Center Bridging) subsystem
>  .RB "[ " dgram-port-prio " ]"
>  .RB "[ " port-prio " ]"
>  .RB "[ " dscp-prio " ]"
> +.RB "[ " pcp-prio " ]"
>  
>  .ti -8
>  .B dcb ets " { " add " | " del " | " replace " } " dev
> @@ -33,6 +34,7 @@ the DCB (Data Center Bridging) subsystem
>  .RB "[ " dgram-port-prio " " \fIPORT-MAP\fB " ]"
>  .RB "[ " port-prio " " \fIPORT-MAP\fB " ]"
>  .RB "[ " dscp-prio " " \fIDSCP-MAP\fB " ]"
> +.RB "[ " pcp-prio " " \fIPCP-MAP\fB " ]"
>  
>  .ti -8
>  .IR PRIO-LIST " := [ " PRIO-LIST " ] " PRIO
> @@ -64,6 +66,9 @@ the DCB (Data Center Bridging) subsystem
>  .ti -8
>  .IR DSCP " := { " \fB0\fR " .. " \fB63\fR " }"
>  
> +.ti -8
> +.IR PCP " := { " \fB0\fR " .. " \fB7\fR " }"
> +
>  .ti -8
>  .IR PRIO " := { " \fB0\fR " .. " \fB7\fR " }"
>  
> @@ -182,6 +187,18 @@ command line option
>  .B -N
>  turns the show translation off.
>  
> +.TP
> +.B pcp-prio \fIPCP-MAP
> +\fIPCP-MAP\fR uses the array parameter syntax, see
> +.BR dcb (8)
> +for details. Keys are PCP/DEI values. Values are priorities assigned to traffic
> +with matching PCP and DEI. PCP/DEI values are written as a combination of
> +numeric- and symbolic values, to accommodate for both PCP and DEI. PCP always
> +in numerical form e.g 1 .. 7 and DEI in symbolic form e.g 'de', indicating that

0..7?

> +the DEI bit is 1.  In combination 2de:1 translates to a mapping of PCP=2 and
> +DEI=1 to priority 1. In a hardware offloaded context, the DEI bit can be mapped
> +directly to drop-precedence (DP) by the driver.

The last sentence about drivers doesn't belong to this man page IMHO.
Besides I'm not sure it's even correct: there is no notion of in-ASIC
drop eligibility here, just mapping between 802.1q priority+de headers
and in-ASIC priority.

> +
>  .SH EXAMPLE & USAGE
>  
>  Prioritize traffic with DSCP 0 to priority 0, 24 to 3 and 48 to 6:
> @@ -221,6 +238,16 @@ Flush all DSCP rules:
>  .br
>  (nothing)
>  
> +Add a rule to map traffic with PCP 1 and DEI 0 to priority 1 and PCP 2 and DEI 1
> +to priority 2:
> +
> +.P
> +# dcb app add dev eth0 pcp-prio 1:1 2de:2
> +.br
> +# dcb app show dev eth0 pcp-prio
> +.br
> +pcp-prio 1:1 2de:2
> +
>  .SH EXIT STATUS
>  Exit status is 0 if command was successful or a positive integer upon failure.